The invention relates to a driving mechanism of a track traveling vehicle having rubber tires and iron wheels on its chassis and which is capable of self-propelling on a track of a rail road as well as on a public road, wherein the iron wheels can be turned by a driving force of the rubber tires.
In a track provided to allow a street car or train to travel thereon, periodical operations are frequently conducted. There are a variety of operations as periodical operations, such as maintenance and inspection of a trolley line that is constructed over the track in addition to ground operations such as tamping of smashed stones paved on the track or change of tiles. In such operations relating to the track, operators and materials need to be moved to an operating or job site, and most job sites normally have no road or traffic access. In many cases a track traveling vehicle (also known as a land track traveling vehicle) capable of traveling on both a public road and a track is used to move operators or materials to an inconveniently situated job site.
The foregoing track traveling vehicle has a body or chassis of a generally known truck provided with rubber tires as its base, and iron wheels provided under the chassis to travel on a track. The track traveling vehicle travels on a public or normal road by rubber tires so as to move to a railway crossing close to a job site so as to move from a standby location in an urban district area to the job site located in the suburbs and is positioned along the track. If the track traveling vehicle enters the railway crossing, it is lifted by hydraulic jacks or the like to be turned at right angles with the road so as to align the track traveling vehicle with the direction of the track. Thereafter, the iron wheels are lowered to contact the rails while the lower ends of the rubber tires are forced to float in the air. In this state, the track traveling vehicle is held by the respective iron wheels so that the track traveling vehicle is moved along the track when the iron wheels are driven. In the track traveling vehicle capable of travelling on both the public road and the track, it can travel on the public road at high speed until it reaches a railway crossing from a standby location of a maintenance or construction company, and can also travel on rails from the railway crossing to a job site, thereby quickly and efficiently moving operators and materials to the job site.
There have been conventionally employed two types of methods for driving a track traveling vehicle having the foregoing construction on rails. The first method is to lift a chassis by iron wheels while the rubber tires of the truck are maintained in contact with the surfaces of rails. In this method, if the rubber tires are turned to travel on a general public road, a driving force or tuning force of the rubber tires moves the chassis owing to frictional force generated between the rubber tires and the rails. At this time, the iron wheels have the function to merely guide the chassis not to come out from the rails, while the motion of the chassis depends on the frictional force of the rubber tires. In the first method, the rubber tires are forced to contact the rails while keeping an appropriate pressure therebetween, resulting in a difficulty in controlling thereof.
The second method is to lift the entire chassis by the iron wheels while the rubber tires are forced to float in the air, then the iron wheels are driven by hydraulic motors connected to the iron wheels. In this method, the speed (i.e. rpm) and turning direction can be controlled by the amount of a hydraulic oil supplied to the hydraulic motors, resulting in a characteristic of easy driving of the track traveling vehicle. There is conventionally employed two ways for sucking and discharging the hydraulic oil to the hydraulic motors. One way is to apply power from a vehicle battery to electric motors, so that hydraulic pumps are driven by the electric motors to discharge hydraulic oil. This way has, however, a drawback in that a large amount of hydraulic oil is not discharged by the power applied by the battery, and energy consumption in the battery is large. The second way is to connect hydraulic pumps to an engine mounted on the chassis and hydraulic oil is discharged from the hydraulic pumps by the turning force of the engine. In the second way, the tuning or driving force of the engine can be directly transmitted to the hydraulic pumps as it is very efficient, and hence this way is widely employed.
The conventional track traveling vehicle has a mechanism wherein hydraulic pumps are directly connected to an output shaft of an engine, and hydraulic motors are driven by hydraulic oil discharged by the hydraulic pumps, and an output of the hydraulic motors drives or turn the iron wheels. This mechanism has not employed fixed discharge amount hydraulic pumps, but employs variable discharge amount hydraulic pumps (for example as disclosed in Japanese Patent Laid-Open Publication No. 11-189155). These variable discharge amount hydraulic pumps function to control the amount of hydraulic oil that is discharged by controlling a control pressure even if the output of the engine is constant. If variable discharge amount hydraulic pumps are used, the discharge amount of hydraulic oil can be varied by stages from zero to the maximum by controlling a control pressure so that the hydraulic motors, namely, the rpm of the iron wheels can be varied by stages by controlling the amount of discharge of hydraulic oil from the hydraulic pumps. In such a control method, there is an advantage that the rpm of the iron wheels can be varied smoothly from zero to the maximum, and also the controlling operation is easily made to smoothly drive the track traveling vehicle. However, the variable discharge amount hydraulic pumps are expensive in cost and complex in hydraulic system piping for controlling purposes. Further, since the variable discharge amount hydraulic pumps are fixed to the chassis side, and the hydraulic motors for driving the iron wheels are fixed to the rear portion of the chassis, there is a drawback that the length of hydraulic piping for connecting the variable discharge amount hydraulic pumps and the hydraulic motors becomes long because these pumps and the hydraulic motors are connected by a hydraulic hose or the like. Accordingly, the conventional variable discharge amount hydraulic pumps have many drawbacks in view of cost and design thereof although they are excellent in operability.
The driving mechanism of a track traveling vehicle of the invention is characterized in a construction that hydraulic pumps are driven by rubber tires of a generally known truck that forms a base of the track traveling vehicle, and hydraulic motors are driven by hydraulic oil discharged by the hydraulic pumps. With this construction, a driving force between an engine and a transmission is transmitted to the rubber tires to operate the hydraulic pumps as it is without altering or reforming the driving mechanism of the truck. It is possible to suck and discharge hydraulic oil in the same manner as in an ordinary truck, and the turning output of the engine is changed to effect forward and backward operations or stopping operation. Further, since the driving mechanism of a track traveling vehicle can employ cheaper fixed discharge amount hydraulic pumps without using expensive variable discharge amount hydraulic pumps, the mechanism becomes cheaper in cost.
To achieve the above objects, a driving mechanism of a track traveling vehicle according to a first aspect of the invention capable of traveling on both a road and a track comprises front and rear rubber (i.e. road) tires supported by a chassis at the lower portion thereof, front and rear iron (i.e. track) wheels supported by the chassis and movable vertically, hydraulic pumps and hydraulic motors, wherein the track traveling vehicle travels on the road when the iron wheel are lifted while the front and rear rubber tires are forced to contact the ground, and the track traveling vehicle travels on the track when the front and rear iron wheels are lowered to contact rails while the front and rear rubber tires are forced to float in the air (i.e., in a raised suspended state out of engagement with either the road or track), and wherein the hydraulic pumps are driven by the rear rubber tires so as to suck and discharge hydraulic oil to the hydraulic motors, and the front or rear iron wheels are driven by the hydraulic motors so that the track traveling vehicle travels on the track.
The driving mechanism of a track traveling vehicle according to a second aspect of the invention is characterized in that the driving mechanism of the first aspect of the invention comprises a swing portion fixed to the chassis and arranged to be vertically swung by hydraulic cylinders, friction wheels supported by the swing portion and capable of contacting rear rubber tires at the peripheries thereof when the swing portion is turned, and the hydraulic pumps being driven when the friction wheels are turned.
The driving mechanism of a track traveling vehicle according to a third aspect of the invention is characterized in that the driving mechanism of the first aspect of the invention comprises a swing portion fixed to the chassis and arranged to be vertically swung by hydraulic cylinders, an axle supporting portion fixed to the swing portion at the lower portion thereof, the rear iron wheels supported by the axle supporting portion at both sides thereof, and the hydraulic motors provided on the axle supporting portion for driving the rear iron wheels, wherein the swing portion and the axle supporting portion are turned when the hydraulic cylinders are operated so that the rear iron wheels supported by the axle supporting portion are forced to contact rails to allow the rubber tires to float in the air.
The driving mechanism of a track traveling vehicle according to a fourth aspect of the invention is characterized in that the driving mechanism of the first aspect of the invention comprises a swing portion fixed to the chassis and arranged to be vertically swung by hydraulic cylinders, and an axle supporting portion fixed to the swing portion at the lower portion, wherein the axle supporting portion is connected to the swing portion so as to be vertically laterally swung (i.e. to the left and right).
A driving mechanism of a track traveling vehicle according to a fifth aspect of the invention capable of traveling on both a road and a track, comprising front and rear rubber tires supported by a chassis at the lower portion thereof, front and rear iron wheels supported by the chassis and movable vertically, wherein the track traveling vehicle travels on the road when the iron wheel are lifted while the front and rear rubber tires are forced to contact the ground, and the track traveling vehicle travels on the track when the front and rear iron wheels are lowered to contact rails while the front and rear rubber tires are forced to float in the air, wherein said driving mechanism further comprises hydraulic pumps for driving use that are driven when the rear rubber tires are turned, hydraulic motors that are driven by hydraulic oil discharged by the hydraulic pumps, and a hydraulic pump for oil supply use that is driven when the rear rubber tires are turned, wherein two hydraulic circulation circuits are formed by connecting and closing both hydraulic output ends of the hydraulic pumps for driving use and the hydraulic motors, and wherein a hydraulic output end of the hydraulic pump for oil supply use at the discharge side communicates with the hydraulic circulation circuits, so that two hydraulic pumps are driven at the same time when the rear rubber tires are turned to discharge the hydraulic oil, thereby supplying the hydraulic oil that is discharged from the hydraulic pump for oil supply use to the hydraulic oil circulation circuits.
The driving mechanism of a track traveling vehicle according to a sixth aspect of the invention is characterized in that in the fifth aspect of the invention, the number of hydraulic pumps for driving use is two, and the number of hydraulic motors for turning the rear iron wheels is two, and the number of the hydraulic pump for oil supply use is one, wherein the three hydraulic pumps are operated at the same time when the rear rubber tires are turned, and wherein the hydraulic pumps for driving use are connected to both hydraulic output ends of the hydraulic motors to form two hydraulic circulation circuits, the hydraulic output end of the hydraulic pump for oil supply use at the discharge side communicates with the hydraulic circulation circuits, and wherein hydraulic oil discharged from the hydraulic pump for oil supply use is supplied to the respective independent hydraulic circulation circuits for turning the hydraulic motors.
The driving mechanism of a track traveling vehicle according to a seventh aspect of the invention is characterized in that the hydraulic circulation circuits of the fifth or sixth aspect of the invention are formed by connecting and closing both hydraulic output ends of the hydraulic pumps for driving use and hydraulic motors for turning the rear iron wheels, and a safety circuit is provided between pressure application sides and application collection sides of the hydraulic circulation circuits for leaking hydraulic oil of one hydraulic circulation circuit to the other hydraulic circulation circuit and discharging overflowed hydraulic oil when hydraulic oil exceeds a prescribed value.
The driving mechanism of a track traveling vehicle according to an eighth aspect of the invention is characterized in that in the fifth or sixth aspect of the invention, both hydraulic output ends of the hydraulic pump for oil supply use communicates with an oil tank via check valves directed in a forward direction, and also communicates with the oil tank via relief valves directed in a forward direction, and is further connected to both hydraulic output ends of the hydraulic pumps for driving use via check valves directed in a forward direction.